


Paracords

by skerb



Category: Undertale (Video Game)
Genre: Body Worship, Consensual Kink, Don't copy to another site, Ecto-Tongue (Undertale), Established Relationship, First Time, Heavy Petting, Kinda, Kissing, M/M, Making Out, Miscommunication, Multiple Orgasms, Multiple Penetration, No Ecto-Penis (Undertale), Overstimulation, Praise Kink, Sacrum Lacing, Sanscest - Freeform, Sensitive bones, Size Difference, Soul Sex, Sub Sans (Undertale), Undertail, Undertale Monsters on the Surface, kustard - Freeform, ready your kink bingo card, weird monster customs
Language: English
Status: Completed
Published: 2019-01-04
Updated: 2019-01-04
Packaged: 2019-09-13 22:36:10
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 9,371
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16901112
Author URL: https://archiveofourown.org/users/skerb/pseuds/skerb
Summary: When Sans approaches Red with a proposition, Red takes it the wrong way. Miscommunication leads to Sans' first time being tied up. (Sacrum lacing, that is.)





	Paracords

Just how was he going to explain this? Sans wasn’t sure, but he did know the devious expression that had passed over Red’s face when he had suggested sorting his laces. Had he missed something? Unwittingly invited the other skeleton’s innuendo? Perhaps it was just something that he found humourous for whatever reason.

And yet he couldn’t shake it. He had only mentioned that he had some ‘laces to sort through’ and it would ‘take a lot of time to do it by himself’. What exactly had sparked Red’s giddy and even sultry expression at hearing such a thing?

Surely, he was missing something.

Of that he was certain, naturally, when Red followed him upstairs shortly after. Sans kept himself composed, not giving any sign that he was perplexed by the skippy little steps his counterpart took upstairs and down the hall. Nor did his soul jump a little when, as he fit the key to his door’s lock, Red’s arm snaked around his torso. That would just be  _absurd._

Although, absurdity was a coping mechanism Sans had fallen into routine with over the past few years. With Red, it was the only way his devious nature - while he was in fact a sweet and doting ass - had that roguish charm he just came to love. So despite being so utterly confused, he allowed Red to follow him like an excited puppy into his room, where he had all but shed his leather coat in three seconds flat.

“you’re really adamant about this, huh,” the smaller of the two murmured under his breath with a vague shrug. He looked to the skeleton in front of him, his eye lights following the thicker and stockier form than what he was used to with his own body.

“always up to helpin’ a  _friend,”_  Red replied, his sharp grin widening while Sans rolled his eye lights. While it was no secret the two were sweet on each other, Sans’ early-relationship insistences that they were ‘friends’ was enough fuel for Red to tease him at every possible conjuncture.

Including now, when he could switch from being the sweetest being in the known universe to hinting at more devious endeavours.

“ok,” Sans relented with another shrug, still a little confused. He went to dig out his runners like he’d originally planned.

Since coming to the surface, it was difficult to kick old habits of upcycling what monsters could find for free or on the cheap, and Sans was no exception. He pulled out the box shoved haphazardly between his mattress and the nightstand while Red leered on, only to be caught off guard by something.

Sans could basically see the cogs working in his skull, although he had to figure Red was thinking of something wildly inappropriate instead of… simply re-lacing a pair of sneakers found several yards apart in the park. It had been after a human holiday celebrating the coming of a new year.

Which he found odd. Because years happened all the time, were a universal constant, and it was a little silly in his mind to celebrate something like that. But it meant free food, a lightshow, and humans getting silly and monsters indulging in the local festivities. It was also amongst the handful of times the two of them had been together before anything ‘serious’ had entered either of their skulls, so it held a special meaning for them now.

And of course… that expression Red was wearing. The exquisite small ticks that passed through the phases of his eye lights as realisation clicked into place. If he knew him, or any variation of himself, Red was confused as well. And, because of his vastly different upbringing in his universe, it was likely Red was trying to save face at the same time.

Welp, that made the two of them. It became somewhat of a stalemate, and Sans could practically see the sweat starting to bead on Red’s skull. Smirking to himself, the smaller skeleton shimmied the shoes in the box, the loose laces he’d scavenged from his time in the Underground jostling around in a tangled mess.

“oh, love,” Red breathed out a hoarse laugh and reached down to grab a handful of dirty laces, then dropped them just as fast. “r’these all ya got t’work with?”

Sans eyed him with a challenging look, noting how Red seemed almost piteous in the face of his awesome lace collection. Some were long, some were different colours. Others were hard leather cords (a rarity in the Underground since they tended to wither in their descent into the dump), and there were a few funky neon-coloured, spiral ones.

Although he was a little confused as to what Red meant by his collection, Sans rested his jaw in his hand and watched as his boyfriend took another handful and dropped it right into the box again. With a grunt of affirmation, the stockier skeleton laughed once more, this time his rough voice softer.

“aw.” At this, Sans flushed automatically, knowing the tone. “that’s precious. i don’t mean t’poke fun, babe, but i think i got somethin’ at my place that’s gonna be a bit better than those ratty ol’ things.”

Sans recovered enough to roll his skull upward to give Red the most neutral look he could muster. “oh yeah?”

Red’s grin widened, a peek of gold glinting in the low light, and Sans felt his soul thump harshly with the veiled expression - it was downright  _lewd._ Fuck, he knew that look. No, clearly he had misunderstood something, and this was his only chance to right it by admitting he was wrong.

But this was Red. Sans  _couldn’t_ do that. He shifted uneasily where he sat and Red must have construed the movement for something else entirely, as he discarded yet another handful of laces into the box and took up the string dangling from Sans’ hoodie instead, drawing near.

“i’ve got an idea… how’s about y’sit tight… right here,” Red’s voice dropped in register, and although his confusion continued, Sans felt that his tone was igniting sparks of delight all around his body.

Jeez, this guy could make any situation inviting, Sans thought. Still unsure, he sat, his eye lights lowered to the corded string Red’s digits held loosely, slowly allowing it to slip from his grasp.

“uh… ok,” Sans murmured between them, his voice sounding soft yet tight. He swallowed thickly when Red finally pulled away, giving him enough space before immediately turning and disappearing.

His soul thrumming hard from the sudden close proximity and still wondering just what the  _hell_ had transpired to spur that reaction on, Sans stared at the box of laces before covering it again and shoving it out of the way. Whatever Red had planned, it probably had nothing to do with his shoes. That was what he hoped, anyway. It would be amongst a few of the man’s more interesting preoccupations, if that were the case.

As he awkwardly waited, he took up the box again and pulled out one of the shoes to untangle the knots while his boyfriend was away.

 

Soon enough, Red returned with a box of his own. Sans could never get used to the fact that his counterpart could  _also_ teleport, but he had at least managed to stop himself from jumping every time. Now, however, his soul kick-started anew when he felt the surge and heat that came with his lover’s magic - and what it meant for the unbidden promise Red had in store.

Instead of focusing on that, Sans’ eye lights settled on the small, worn and creased box that Red held in somewhat of a death grip. When his gaze flitted up, he saw that Red’s look had morphed into something a little more demure, and was that… a blush? Sans could swear he was a little taken aback, but this definitely took the cake.

“practisin’ while i was gone, eh?” Red observed, now obviously bashful.

Yeah, Sans was definitely missing out on what was going on. He set the shoe down as he hadn’t really gotten anywhere with untying the laces tangled in it and he tilted his head.

“ok. this’s gonna sound really, uh… weird. but, i’m not quite sure i understand what’s goin’ on, for starters-”

 

Red idly scratched the back of his leg with his shoe, pausing for a moment to take in the open box next to where Sans was seated on the bed, and how he looked so…  _nonplussed_ about everything. Did he really not care? Was it nothing to him?

Starting to backpedal a little in his thoughts, Red approached to look into Sans’ box of laces again with something of disdain. This collection didn’t even have  _aglets._ How the hell was he supposed to get anything done that way? Perhaps that’s the reason why Sans had (more or less) approached him for help. Maybe because he was having a hard time on his own, he needed help, or-

Red nearly dropped his box of goodies and restrained a shocked gasp. Maybe it was the little guy’s  _first time?_

Oh, this was going to be  _perfect._ He now had no doubt that had been anything but the case. Not that he hadn’t drawn the same confusion when it came to Sans giving him some right-foot socks, or can tabs that had been used for makeshift currency in this world’s Underground, or any other weird cultural differences.

Sacrum lacing had to be a universal constant, right?

Far be it for him to think otherwise - Red came from an instance where there were many skeletons and it was widely known. What other conclusion could he draw that Sans wouldn’t have known any other way?

They were boyfriends, after all. It was definitely something that was done between partners. And there Sans was, his smaller body hunched inwards as though to hide the fact that he was very much trying to practise on that shoe. It was cute in a way, if a little perverse… but that made him all the more endearing.

“uh, you… you ok there?” Sans asked quietly, toying with the lace between his digits as the silence extended. His feet idly tapped on the carpet and Red forced himself to move, seating himself next to the smaller skeleton and thrusting the small box into Sans’ lap.

Red’s face definitely couldn’t feel any hotter. His soul pounded furiously inside of his chest when his alternate gave him a quizzical look, then slid the bent lid off the top to peek inside.

“s’my, uh… `collection`,” Red murmured, embarrassed.

 

Sans felt like the admission was more as though Red had just revealed some sort of perverted toy assortment, but what greeted him was a collection of laces much like his own. Some shared the same colours as his own: neon greens, oranges, spirals, thick cords, braided silk, some ribbons and metal-capped aglets; some even had glittering beads. In fact, most  _did_ have either a hard metal clasp on the end or a piece of plastic, although Sans noticed something peculiar.

“m’not seeing many pairs,” the smaller skeleton noted after pulling several lengths from the worn kraft box. They all appeared in relatively good shape though. Sans figured it was due to the fact that his counterpart’s CORE had been established much later than his own, thus they had to craft everything by hand. A lot of the braids were elaborate and some even had multiple strands in different colours. “actually… not seeing  _any.”_

Red was tense next to him, but his eye lights seemed to shrink in surprise at the expressed concern. It was slowly beginning to dawn upon him what exactly Sans might be thinking - or if he could discern it at all, maybe-

“red, i think this’s the sock fiasco all over again,” Sans finally chuckled, lightly. “that, or some very elaborate prank. either way, you stumped me, so…” He placed the laces back into the box and couldn’t help but feel envious as to their delightful construction. Then he leaned his skull against the taller skeleton’s shoulder. “good one, man.”

Red’s soul was still pounding furiously. No, while this was something he could easily save face with, he was just  _thinking_ of all the interesting things Sans had indulged him in lately. While Sans was pushing his weight against him, Red thumbed through the collection of long cords, lace and ribbon, selecting one that was a powdery rose, outfitted with a couple of engraved cylindrical clasps at each end.

Cautiously, he snaked an arm around Sans’ shoulders and held him close, bringing the selected ribbon to the forefront of his boyfriend’s vision.

“it ain’t a prank, or joke, or… anythin’, really, doll,” Red murmured. “n’fact, if yer willin’ to entertain me, m’sure i’d be able to make it worth your while…”

Sans laughed against him, turning his skull against Red’s shoulder and pushing himself closer. “you’re  _stringing_ me along, here.”

Red’s laugh was like a sudden bark in its defensiveness, “who  _me?_ nah, sweetheart.” He paused as Sans buried his face against his shoulder all the more. Red just  _delighted_ in the way that his counterpart was bashful at his little pet names, even after all this time. “y’see, i think i’m gonna be learnin’ ya somethin’ real fine today,” he purred, his tone making the magic driving through Sans’ bones prickle with anticipation. “ye curious?”

He saw the flush of cyan against his lover’s bones when Sans moved to inspect the rose ribbon, glaring at it as though it were offensive. Red reconsidered it the more he played with the ribbon’s metal aglets, then returned it to the box to search for something else. It caught Sans’ curiosity for sure, his eye lights trained on the mass of laces while Red watched.

“kinda weird.”

Red felt his soul plummet with the rejection and his hand stopped before he could prevent himself from reacting.

“but ok,” Sans shot him a sneaky wink and immediately he felt his soul spark with affection and excitement. “you seem pretty into… whatever this is. macramé?”

While there were a few cords in the box that Red had - believe it or not - woven himself, he wouldn’t dare to reveal that just yet. Instead, his face beaming a hot shade of crimson, he selected a plain blue string with blunt aglets at the ends. He thumbed them, feeling a little shyer, until Sans moved to kiss him.

“heh. what a crafty guy,” the smaller skeleton murmured, making Red flush all the more. “ok. explain to me what’s next.”

Red moved to press their teeth together in a kiss, one hand sinking lower to run against Sans’ ribs through his shirt. It elicited a deep sigh from Sans with another chuckle, and soon his lithe digits were braced against Red’s clavicles.

“drop trou.”

“uh…” Red was sure he felt Sans’ face get hot and he could literally see his confusion now, with a clarity only their proximity would allow. Sans shifted in his hesitation, but he didn’t move to do as instructed while Red moved the box to the floor. “and… why? just outta curiosity…”

Red figured he had to be upfront with his knowledge instead of cagey, unlike their previous indulgences. He gave Sans’ vertebrae a soft nip and ran his tongue over the spot, eliciting a surprised inhale, then another slight and breathy chuckle.

“ah, i gotcha. one of `those` days, huh,” Sans murmured and returned another kiss, moving to unzip his hoodie and straddle his boyfriend’s lap. Red felt a tingle slip down his spine when Sans let his hoodie drop behind him, using him as leverage to ensure he didn’t fall. His joints glowed with the softer features and magic unknown in his world, and Red could just feel the amount of love and affection Sans practically beamed at him.

Since it was in all likelihood Sans’ first time, Red eased him into it, every kiss lingering just a little, stealing breaths long enough to make Sans pant. The more Sans’ hands roamed, the more Red returned the touches, fleeting, tender, tracing every smooth line and curve over Sans’ pristine bones until he started to feel achy in just the right way.

Red moved them over towards the centre of the bed to ensure they wouldn’t lose balance and topple off the side, his own breaths deep and urgent with Sans’ eager, soft sounds. He squeezed Sans’ hips, applying a light pressure to convey his intent, magic seeping into Sans’ bones enough to heat them and make him groan needily against Red’s collar.

“it’s pretty intense, just fyi,” Red panted, the cord in one hand as he slowly pushed up Sans’ shirt to expose his lower ribs.

Sans’ eye sockets were lidded heavily, mouth agape as every inhale was deep and excited. Red saw the flash of confusion pass through his features, but it quickly melted away when he caressed the column of Sans’ spine. Sans hummed with a quiet little laugh, his rib cage heaving when the taller skeleton allowed the tips of his phalanges to glide down every notch and space in each vertebrae, stopping just before his sacral plain.

The smaller skeleton lifted his hips when Red tugged at his waistband encouragingly, keeping an arm slung around his neck in order to keep close. He was flushed and panting, wanting more of whatever Red had in store for him, as long as it felt good. And it would feel good, he just  _knew it,_ because Red always made sure their time together was tender and loving, strengthening their bond with every caress and softly spoken word.

Once his track shorts were pulled down halfway, Red gently grasped under Sans’ tailbone, eager to continue. It pulled an indignant and surprised grunt from the smaller skeleton, who instinctively held on as Red manoeuvred him with one arm, slowly pulling the unwanted clothing away to be tossed aside.

“now,” Red purred as he settled Sans down on his back against the mattress, hovering over him as he drank in every detail of his boyfriend’s half-naked frame. He felt his soul tremble as Sans pulled him closer, fingers latched on to one of his clavicles as leverage, tongue conjured to taste the magic between them. It trickled all the way down to his pelvis, causing him to shift to obscure his arousal.

“this’s all about you, hun,” the larger skeleton murmured as his grip went a little lower, his fingertips grazing over the subtle shifts and raised surfaces in Sans’ sacrum.

Sans muffled a low whine and nodded, a blissful smile overcoming him as he arched up to the touch. “you always make it about me,” he muttered wryly, then his expression shifted slightly when Red moved closer, bringing his femurs up towards him so that he was awkwardly straddling his lap while laying on his back.

Flushed, as Red had a prime viewing spot of his pelvic girdle, Sans laughed a little shyly. “m’not anywhere near your, uh…” He flushed more, cyan suffusing his bones when his eye lights dropped past his own pelvis to Red’s - still clothed, unfortunately.

A shudder passed through his body when Red didn’t answer, instead beginning to rub pressure against the flares of his hip bones, kneading an incline of pleasure that only increased the further inward Red’s fingers moved. Sans couldn’t help but buck up the closer his lover’s hands got to his sacrum, hot, longing sighs escaping him as his excitement built up. He could feel the tingly hot throb of magic begin to build up in the void of his pelvis, but more importantly, how the cord Red had in one of his hands tickled the right side of his ischium.

While it wasn’t worrying, it was a little bit of a distraction. Did Red mean to tie him up with it, or was he playing at some kind of game? Panting heavily with Red’s ministrations, Sans looked up to Red’s kind expression and was soothed by it, giving way to more delightful little shivers that trickled all throughout his body.

No, he definitely wasn’t up to anything, prankwise. It would be just another lazy afternoon, making love, relishing in each other’s arms with nothing but a doting lover and a calm respite. Sans couldn’t help the pleased smile that came over him, a low moan coaxed from him when Red’s fingertips flitted over the foremost gaps between his hip bones.

He was gentle and Sans loved it, loved  _him,_ urging him a little more with a huff and an eager nod. He closed his eye sockets as fingers travelled down to the next one, mapping out in excruciatingly blissful circles before going down to the next pair of holes. He clutched at the sheet on the mattress with his free hand, his breathing starting to come in quicker the longer Red toyed with him, trying not to outwardly beg for what they both knew he wanted. He bent his legs, his toes pushing against the mattress in order to gain leverage to grind helplessly against his lover.

“please-” He couldn’t help it. Sans had been spoiled by Red and he honestly held out for as long as he could. He just wanted to be touched all over by him, to be given whispered praise and secrets Red only dared to share with him when they were alone.

“arright. y’ready?”

Sans felt a flood of desire course through him with that and a hushed chuckle escaped him as he nodded in affirmation. He was excited, his soul trembling and pulsing with magic to prepare himself to accept whatever love Red had to offer.

As he did, again, he felt the tickle of the cord and Red’s hands moved. One of them cupped behind his tailbone, while something was introduced to the lowermost foreside of his sacrum. Sans inhaled sharply with the prod against the space; it felt foreign, especially without the usual magical heat that Red’s hands normally had.

There was more pressure as the tip of whatever it was brushed against the interior foramen. He released a startled squawk and his soul seized in confusion, his legs tautening more out of reaction than anything done consciously. It had felt intrusive yet subtle, brushing against the hidden surface that even he couldn’t reach. It pulled another shout from him and he tensed more as pleasure stung at the spot, but Red didn’t continue…  _whatever that was._

It felt like nothing he had ever experienced before, but it wasn’t unpleasant. Quite the contrary, actually. He was just shocked from the sudden… entry? Another throb of ecstasy made another embarrassing noise leave him when the tip of whatever-it-was left the sacral hole, leaving the magic-infused bone heated and flush at the brief probe. When Sans reopened his eye sockets, Red actually looked  _alarmed._

“wh.. what  _is_ that!” Sans exclaimed, struggling to get up to inspect his pelvis. He saw the confidence melt from Red’s expression to one of dumbfounded puzzlement.

“lacing?” Red offered, as if they were on the same page this entire time. He withdrew his hand from Sans’ sacrum, his own face burning.

Sans’ breaths evened out as he pushed himself onto his elbows to see the unassuming blue length in Red’s grasp, thinking things couldn’t possibly make any less sense then than it had before.

“what.”

“whaddaya mean, `what`?” Red said sheepishly, as though spurned. “i mean… this’s what y’were gunnin’ fer, right?”

“what?” Was there an echo flower in the room? Sans blinked up at him, starting to calm.

“lacing.” Red’s tone was sounding less and less sure the more he spoke.

Sans blinked. No, there  _definitely_ was an echo. The longer he paused to absorb the situation or what exactly ‘lacing’ meant, the more awkward the situation would become. Thickly, he swallowed, not at all opposed to the sensation - he just was, well… a little thrown for a loop for what Red had meant with his proposition.

“oh,” he sighed, amusement in his tone as he attempted to salvage the mood. “kinky,” he added with a wink, letting his tailbone ease back onto Red’s lap where he could  _definitely_ feel the heat of magic coalescing in his pants. He allowed himself to relax a little when he saw Red’s shy smirk and the way he shrugged as though in dismissal. He gently caressed Red’s ulna as he relaxed a little more. “uh, wanna explain?”

Red’s flush deepened, his soul thumping hard with the curious tone. His smile was wide and his eye lights couldn’t settle anywhere further than Sans’ sternum, absorbed with how clean and unmarked it was.

Sans exhaled hotly, running his hand up and down the length of the other’s ulna, then moved a little over the side to rest his hand on Red’s femur. “think i was startled, but c’mon… i’m curious,” he persisted, his tone levelling out with a roguish lull that hummed in just the right way. “i know you’d never hurt me. `cause you  _love_ me.”

That did something. Red’s grin widened with the reassurance and he bent over Sans for a kiss, leaving a hot trail of magic in the place he was admiring before.

“arright,” he said again, sounding a little more confident than before, “a lil’ history lesson, then.” He grabbed Sans’ hips with his hands, resuming the tingling pulses with each deft rub of his thumbs. Sans rewarded him with an excited shiver and huff, leaning back onto the mattress to allow himself to be pampered.

“s’already pretty much well-known there’s a lot more skeleton monsters in our universe than yours,” Red resumed, his gaze drinking in the state of arousal his lover was in, who unsuccessfully quelled any muted hums that left his parted teeth with his movements. “different monsters have their own ways of havin’ fun… so our kind made our own. you say macramé, but you’ve only just touched upon the  _knotty_ parts. the true  _knitty_ gritty.”

Sans covered his mouth with one hand and held back a mewl of pleasure when Red’s hands manoeuvred closer to his sacrum once more, pulsing throbs heightening as he was closed in on from both sides. He gave a nod to show he was listening, but  _god,_ how was he supposed to focus on such a tale while  _this_ was happening?

Red took up the length of blue again and dragged the end’s aglet around his lover’s lower spine once, relishing in the way Sans’ pelvis jolted when he allowed it to trail over the crest of one of his hips.

“we’re pretty decent weavers, y’know… braids, cords, cloth,” Red trailed off and gently pulled the opposite end of the piece to catch on the spines of Sans’ lower vertebrae, causing him to gasp in surprise. “an’ of course…  _lacing.”_

Sans nodded to show that he understood, feeling flush as he opened an eye socket to watch the careful, teasing little touches that were causing him to fall apart in the best way. His affirmative hum was more like a whimper of delight and he could feel how the slick lace slithered around his bones like fine silk. The more Red uttered the word ‘lacing’, the more he hungered for a demonstration.

Red was breathing deeply, his own excitement at seeing Sans so wound up over his words enough to have his own magic reacting.

He gave in to a long sigh, then continued; “it’s pretty intense, sweetheart… didja wanna try? through one hole, out an’ in through the other… and up…” Fuck, his body was starting to heat up, watching Sans’ hips involuntarily twitch with his explanation. The smaller skeleton’s eye sockets were closed again - no doubt imagining what he’d do to him, Red thought.

So he leaned up for a better view, his sharp phalanges gently stroking the flare of Sans’ hip. Sans peeked at him, a dim glow shifting below his ribs with the gentle yet nervous nod of consent.

Red had to inwardly attempt to not give in to the sudden thrilled grin that threatened to crack his face. Instead, his soul was pounding a mile a minute while he carefully brought his hand grasping the cord to the forefront of Sans’ sacrum again. The smaller skeleton inhaled sharply, his breath releasing in a shudder as Red caressed his spine, soothing him as he introduced the tip of the lace into the lowest gap.

Sans’ voice cracked on a gasp with the reentry, even if the aglet didn’t quite fit. Red gently pushed his free hand up to caress Sans’ heaving ribs, following the curve of the bones down to his spine again. He saw the beat of Sans’ soul and the pretty light that accompanied it. The construct flickered erratically when he rocked and encouraged the tip into the space and out the other side.

With Sans’ muffled whine, Red grinned down at him. “there ya go. y’got this, sweetheart. look at ya, bein’ so good,” he cooed, watching as Sans’ face contorted through several stages of surprise and pleasure.

“feels big,” Sans whispered stutteringly, his hand reaching out to grab at Red’s femur again. A shiver started in his shoulders and slipped down, quaking his body. “w-wow, mmh… heh, whoa-” He covered his face with his free hand, back arching as the tip finally pushed through. His chest rose and fell haltingly, his panting audible as Red waited for him to calm down. He appreciated it, as the spot throbbed, his magic coiling around as it couldn’t weave around the disruption.

Red shifted his position ever so slightly and Sans’ mouth hung open, a hushed sound escaping him when he felt the intrusion move. It tickled and throbbed as it turned in the sacral foramina, sending little signals of pleasure racing up and down his body.

Restraining whimpers, Sans exhaled slowly and uncovered his eye sockets to peek at his lover, just as flushed as he was. He felt a flutter in his soul when Red leaned down to give him another kiss. Soft pecks grew longer, more urgent in the reprieve, that Sans was sure it was Red’s idea to do only that and nothing else.

That is, until he felt a miniature tug on the other side of his sacrum and he gasped into the next kiss, grabbing at Red’s shirt as there was a keen sliding sensation. It was agonisingly slow and smooth, gently rocking from one side of the small space to the other as Red carefully pulled the length of string through, relishing in the way Sans’ body twitched and his voice broke on harsher, higher gasps.

“red-” he pleaded, his voice barely registering as he called for more, his breaths whispering his eagerness. He pulled more at Red’s shirt, magic flooding down into the void of his pelvis, only to scatter once more. He groaned and buried his face into Red’s shoulder, unable to keep himself from shouting out when Red gave the unassuming little string a slight and sudden tug.

_“--hah!!”_

Becoming unbelievably aroused by the repeated sounds of ecstasy, Red pushed Sans down again, taking in the way his lover’s soul was beating furiously, shedding light like a flickering blue flame. He stroked over his sternum, guided by Sans’ urgent grip and the way his leg cinched around him to bring him close.

Sans laughed breathily when Red reached up to caress his face, still keeping a sure hand on the small blue length between them. He waited as he looked on in adoration, wanting to absolutely spoil Sans in every way.

Well, in what better way than to show him how much he cared in the best way possible?

Sans had spread his legs to accommodate Red’s body, toes curling as every shift and movement of the little blue string made his magic pulse in gratifying ways. A surprised gasp was always ready, lower moans being discarded for attempts to keep his voice down when Red introduced the tip to the opposite side of his sacrum and the next hole up.

His mouth hung open as his mind focused on that spot, the tip sliding to one side as the silky-smooth surface grazed over inside, agonisingly sweet as it pressed through into the void of his pelvis again. His fingers flexed into Red’s shirt before he realised that he had been entranced by the sensation, almost paralysing him with pleasure.

“a.. ah! -  _ohmygod-”_

“there you are… good boy,” Red purred as he gently wiped away a tear from Sans’ face. “tell me how it feels, mm?”

“sss-” Sans stopped with a sharp whimper, his shoulders hiking up when Red gave the cord a slight twist in his hand, “so good..! it’s.. it’s  _really_ good, re.. red, wh.. what the  _hell---ee-!!”_

Red did not give him another reprieve as he had before, crossing the lace to the upper-most foramen as Sans babbled helplessly under him. He was starting to sob softly, his phalanges clinging to him and tugging insistently as every insertion and movement unwound him a little more.

“safeword?” Red asked cautiously, giving Sans a moment to recover. He leaned back while Sans’ grip on him lessened, panting hard and his bones gleaming with sweat while tears started at his eye sockets.

Sans shook his head from side to side, the action looking a little overwhelming as he took a moment to collect himself.

“g, go ahead,” he murmured rawly, his body practically melting when the length was dragged through to tighten the slack. As he did so, Sans’ phalanges moved to scratch at the sheet, his spine arching with every distinct vibrating little tug.  _“oh…”_

“three down,” Red huffed, shifting again. “y’look so beautiful like this…” he added, his other hand caressing Sans’ jaw, gently running his fingers down to smooth over his heaving sternum. “how’s yer magic feelin’? tell me…”

“mmfhh…” Sans drew a hand across his mouth, his eye sockets fluttering closed when the gliding sensation paused. His hips moved with the memory of the feeling, his other hand venturing down to hover just over his sacral plain, as though he wanted to gauge what it looked like but was hesitant to touch. “like… it’s…  _haa,_ tryin’ t’form… but-”

With the pause, Red’s soul fluttered at the bare mewl that escaped Sans, then he saw a more conscious effort into forming his magic. Pretty cyans and cobalts flowed from the petit monster’s joints to collect down, heating every surface and suffusing it with magic, only to break again. Sans made a harsh noise of frustration, his phalanges flexing so close that it was strummed once with a startled huff.

The larger skeleton leaned back a little to survey his work, which in effect only looked like the tail end peeking out from the lowest gap on the right side, and a diagonal string leading up to the uppermost right side. Sans had relaxed a little more into his lap, one finger curled and idly stroking the string, no doubt delighting in the variable shift in pleasure it was giving him by the sound of it.

“three..?” Sans repeated quietly, the tail end of the word laboured with a shuddering exhale.

Red’s expression softened as he traced his fingertip over a prominent bead of sweat on Sans’ ulna, watching as Sans’ eye lights sought out his own. He looked beautiful; so put on edge, but not yet begging. He was savouring every shaky gasp, every blessed little sound of appreciation that Sans offered up to him for his efforts.

“outta eight,” the larger skeleton replied lowly, his hands seeking out the flares of Sans’ hips with a gentle squeeze. Sans’ eye sockets fluttered with a breathless sigh, his own hand moving to clasp over Red’s at his right side. “y’ready for more, sweetheart?”

Gaining satisfaction from the gentle nod of affirmation, Red lined up the next foramen with the tip on his blind side, just below the last. It was a little bigger than the rest, but it would feel just the same in the end. Sans was watching him, he noted, eye lights wide and hazy as he followed every movement. Then he looked up and their gaze met, Sans holding it as Red leaned in to the penetration, as though it were an extension of himself.

_“ngh!”_

Red could feel the shudder that passed through Sans’ frame when the piece slid into place. The vibrant light from Sans’ soul throbbed in intensity coupled with the twitching hold his legs had on each of Red’s sides. The trembles of orgasm fluttered down the smaller skeleton’s shoulders and settled into his spine, a slick of magic trickling from under his ribs.

“aw, babe… not even halfway done an’ you were already so riled up,” Red teased in a rolling purr as Sans brought an arm up to wipe over his sockets with a shy, raspy laugh. What caught him so off guard was that Sans had  _actually_ lasted this long… when Red himself had only managed two insertions before his own first session had come to an abrupt end.

Sans was still laughing to himself though, watching his counterpart’s doting expression while his hips were caressed. Then the smaller skeleton gave him a wink after having caught second wind, still wiping at a few tears that had welled up in his eye sockets from being so overstimulated.

“better finish up then…”

Red swore that he fell in love with Sans all the more at that moment, like an arrow through the heart. Sans simply huffed at him, balled fists on the sheets as he moved up to see his pelvis and the intricate work being done there. He was careful, oh so careful in not disturbing the wraps that clung to his body in just the right way.

The larger skeleton eased him down, deserting the implement of sweet delicious torment for now to help Sans keep steady. The sheet shifted under his tailbone, gently tugging at the string, and Sans cried out sharply through the pleasure he felt.

“easy there, sweet… y’got this,” Red murmured lustfully between kisses that travelled from Sans’ teeth, down his jaw and lower. Sans panted raggedly as every kiss ignited on the spot, torn between stifling himself by burying his face against Red’s clavicle or to bite down on his shirt. When Red moved down lower, his hands deftly rubbing the expanse of heaving ribs down to his spine, Sans couldn’t help but whine needily.

The slick from his soul made Red’s hand glide easily against his bones, heating every surface it touched as Red dragged his grip down the sensitive column. He hummed lowly, cusping on a throaty growl as Sans hungrily moved into his hand. He could feel Sans twitch in his grasp, his soul lighting up stronger and faster as the spent fluids lubricated the way.

Sans was lost to the sensations with pants and groans of pleasure as Red moved down further still, detaching himself from being straddled around the waist. Every fingertip grazed and ignited his desire so completely, he wondered how long Sans would last before he came again?

Putting his curiosity to the test, the larger skeleton scooted backward to line his skull with Sans’ pelvis, ruby tongue darting out to lave against the joint between his ischiums. Red licked deftly with quick strokes, one hand going between his own legs to try to relieve the tightening throb there while Sans vocalised his pleasure and grasped helplessly at his skull. He heard Sans’ voice nearly  _shriek_ and he pulled his tongue away, delighting in the twitches and jerks that surrounded his head that signalled the smaller skeleton’s imminent release.

But then, he got a devious idea. While it was all and well he treat Sans right and to show him how much he loved him with every capacity that he did, Red took up the longer length of cord into his mouth and gave Sans a sultry look just as he had glanced down, absolutely debauched. Sans drew in deeper breaths to calm down, leaning back onto the mattress as far as he could go before Red’s skull sunk between his legs again, his tongue flicking over the end of the little blue string with his intent in mind.

If the little sacral gap was too small, fitting the aglet in wasn’t made any easier by Sans’ sudden thrash in response to the nudge of his tongue. Red brought it closer, the tip of his tongue probing around blindly to fit it inside, driving the smaller skeleton to keening desperately and kicking out his legs to dig his heels into the mattress. He tasted so sweet, his bones heaving in just the right way under his skill… Red was addicted to everything that Sans was.

He hummed lowly, his voice vibrating down the length as his tongue wetted the piece, hot saliva seeping into the sacral vent as it was finally pushed through. Sans shouted above him, devolved into a twitching mass of hoarse gasps and tears.

Leaning back up to survey his work, Red then captured another sweet kiss. Between them he carefully pulled it through, so slowly that Sans’ mouth went slack against his with the glide.

Red allowed him to rest a moment, idly grasping at his clothes, his shoulders, Sans’ fingers flexing as everything felt so raw and unbelievably good. As though driven to extremes, Sans began to chuckle to himself, his voice sounding absolutely exhausted.

“hn.. hmm… five,” he purred softly, contentedly. “you’re gonna break me.”

Red watched his shaky movements and gently hushed him, taking one hand in his to push his teeth against his digits in a tender kiss. “i would never,” he murmured with a throaty chuckle of his own. “you’re doin’ very, very well, love. so good, and such a pretty sight…” He saw the way Sans bashfully turned his head, and decided to continue. His voice lilted slightly, his praise sending shivers up and down his lover’s body with every uttered word. “you want me to… wrap you up in a pretty bow, mm?”

Flushed and breathless, Sans closed his eye sockets, allowing the words to work their magic while he felt Red take up the blue string again. He shuddered in delight when he felt how taut the lacing was, crossing over the first diagonal weft and above the next so it snagged in just the right way. He huffed, his reactions involuntary at this stage, as Red coiled a loop over the second foremost hole in his sacrum on the opposite side.

The way it twisted and moved had Sans crooning softly, the pleasure beginning to ache while Red clumsily worked with one hand. Then Sans let go, clinging to the hem of his shirt to peek over it to see what Red was doing. With his other hand free, the larger skeleton worked his magic around the cord, heating it and weaving it into place, until a small knot formed. Sans’ eye lights widened with its girth compared to the space it was destined for, while Red gave him a knowing grin.

“a flower… for the greatest treasure of my life,” Red mumbled, a flood of magic touching his face and joints as he twirled the knot in order for Sans to see. It was round, tightly and expertly snug, and looked a little like a ribbon rose, but made with gleaming sky blue. Sans couldn’t help but feel touched by that - especially when Red twisted it around, playing with it as though it had a real stem. “but… like any flower, we need a vase to put it in.” His devious grin returned and Sans braced himself, his soul hammering hard in his chest.

The knot had weight to it, but not enough to make Red’s next selection feel burdened. Instead it felt full, while the opposite end dropped through to the other side, Sans could swear he could feel the woven flower curl off of itself, dispersing the twist. He gyrated his hips with the blissful tease, his magic attempting to form once more.

“why-” he choked quietly, “i can’t… my magic…”

Red quietly hushed him, keeping one hand on Sans’ illium while his other sought out the next gap. He realised that in his haste to create the flower, he would run out of sacral vents to complete his design. He kept his disappointed tut to himself, but Sans’ pathetic “please…” caught his attention most of all.

There were tears glistening in his eye sockets, but no safeword. Still, it was difficult for Red to see Sans this way, confused while also heavily aroused, his magic coalescing only to disperse again.

“it’s ok, love,” Red assured him, “perfectly natural under these circumstances… `cause your leys’re bein’ perforated, your magic ain’t gonna channel through, simple’s’at.” He gave Sans’ hip a gentle pat. “safeword?” he dared to ask, just in case.

Sans exhaled a deep sigh, giving another weary shake of his head. “m’ok,” his voice was a bare rasp, “six?”

Red grinned down with the inquiry and nodded, lining up the length of cord once more. He could sense the subtle tremors that were quaking the body in front of him, how even when he brushed the tip of the aglet against the second to last hole, Sans’ hips jerked with a muted hum of delight. He couldn’t imagine how it felt for Sans, but he could also experience it with him. Even if it was a delight beyond all measure, Red could indulge in weaving a few memorable experiences.

The gleam of Sans’ bones was delightful to watch whenever he moved. His spine arched and his arms were taut with the next penetration, his mouth hanging open as a quaver touched his voice, raw and desperate.

Red shifted his hips again. Ignoring his needs and putting Sans first through all this time was starting to take its toll. Once the lacing was cinched up, he carefully pulled Sans upright, peppering his face and neck with sweet, longing kisses.

“wanna have a looksee?”

Sans hesitated, but he looked down after a moment, so careful not to disturb the intricate weave laced into him. His hands latched onto Red’s scapula and collarbone again when he bent his body inward, a long sigh escaping him when the unassuming lines of sky blue came into view.

It throbbed in all the right ways, but somehow just  _seeing_ it made Sans’ bones heat up all the more. A whimper left him when he saw the remaining length in Red’s hand, thumbing the tip as though prepping it once more. He watched as Red’s hand concealed that which made him jolt with pleasure and it disappeared behind him, a wash of heat flooding him as he felt the prod from behind through the remaining free space. Then he could see through his watery vision it peek through and Red gently grasped at it.

Instead of pulling it through smoothly, Red’s little intermittent tugs brought gushes of pleasure that raced up and down his spine, settling briefly in his soul, before sparking in his joints. Sans vocalised his appreciation with harsher, needy groans, every one becoming more higher pitched and louder until the cord was pulled taut against his sacral plain.

He was so close… so close to cumming, it wouldn’t take much more than a sigh against his ribs, Sans thought. He felt so pent up, desperation kicking into overdrive while Red kept a steady hand grasping the length. Sans found that he couldn’t move, his eye sockets clenched shut while he was held at Red’s mercy.

“red… s-sorry to tell you, but… there’s no more room,” Sans shuddered as the barest fraction of a tug sent a thrill up his spine. He almost hiccoughed as he felt the rubbing from Red’s thumb travel down the remaining piece of string and he slid his hand down the expanse of the ribs in front of him, feeling how they heaved deeply, nearly matching his own.

It was as though the thought suddenly came to him, but Sans let it lead to where he could easily reach - the hot mass of magic in Red’s pants. He pushed past the shirt and below, firmly grasping the hard sex that had been all but bumping against his pelvis the entire time, ignored.

Above him, Red groaned against the side of his skull, sending another shock up his spine. Sans laughed breathily, as he stroked down the concealed length, giving it a hearty squeeze. The reaction was instantaneous, sending Red to capturing his mouth and kissing him a little more roughly than usual.

“see? you always make it about me. an’ here you are… just  _suffering,”_  Sans tutted sensually with a squeeze for good measure.

“and m’not done yet-” Red hummed, his sweet grin returning just before burying his face against Sans’ neck.

Sans could feel it, the doubling pressure. Since it was bone, there was no give like with conjured parts. It was rigid yet snug, attempting to fill all gaps and graze against all the hidden nooks and pivots previously undiscovered. He hissed through clenched teeth, holding himself absolutely still as the two ends clashed for space in the final gap. He jolted where he knelt then, straddling Red’s lap, shocked and heavy gasps pushing past the side of Red’s skull as he clung on for dear life.

“wait, red-” he gulped, drawing in air and magic frantically while his lover rocked his hips into his grasp. “it’s, it’s almost-- _haah!!”_  He arched, white pinpricks dotting his vision as he became a bit more grounded and Red stopped.

“aw, babe… is it too much? or d’ya wanna be filled up?” It ignited his desire, another flood of heat permeating his bones as the words washed over him. “i’ll make ya feel so good. you’ve seen it.” Red paused and brought the longer length of it into view, showing Sans the aglet. “look at it. so small. you’d swallow it right up, wouldn’t ya?”

Sans gulped thickly, feeling the residual throb in his bones. It was like he hungered for more, to be penetrated with everything, perhaps with every lace and ribbon Red had in his collection. That made his soul quiver with excitement and he nodded hastily, giving Red’s ischium a tight squeeze for emphasis.

“this time…” Red purred, his voice almost a growl at the same time, “y’gotta do me a favour and help out.”

Sans huffed as another jolt was sent through the string and he waited, hooking his fingers into the voids of the larger ischiums concealed between them. Red’s hips moved forward with an accompanying grunt, but he continued, “you’re so good at this. y’gotta push it through.”

Sans swallowed again, this time following Red’s sultry look down to his pelvis. Red held onto him with one arm while his other hand placed the cord into Sans’ trembling hand, hot breaths being shared between them. Then his hand was guided down, fingers blindly searching for the spot, gingerly plucking every wrap on the way down. Sans whimpered at each one, not even wanting to think of how the intricate weave and even the knot would be removed after all this without his screams of ecstasy concerning their neighbours.

He squirmed on the spot as Red helped him to introduce the tip to the occupied hole, his breaths starting to come in quicker gasps.

“there ya go, nice and steady,” his lover murmured encouragingly, guiding Sans’ hand with his own to ensure the string wouldn’t slip.

Sans huffed as he struggled with it, his fingers shakily pushing the small piece between the penetration and the tightest space in his body. He gave in to a quiet hiss with his efforts, attempting to rock his hips forward to aid the way.

“feels really b.. big,” he gasped, the hand in Red’s pants gripped hard onto the bone. Red grunted above him and Sans could feel the way his magic was coalescing, as though Red was attempting to restrain himself. Sans’ voice broke when Red’s arm encircled him and strummed down the back of his sacrum, plucking each string like it was a guitar, and Sans vocalised every beautiful note without hesitation.

Red reached the bottom-right foramen, rubbing over the sensitive bone with his thumb as he whispered. “don’t you worry `bout that. ye love it big, don’t ya? give it a lil’ push… hit your sweet spot, just… so.” He paused as another shudder wracked Sans’ body, “i’ll be here to catch ya on the other side.” For emphasis, Red swirled the tip of his finger against the aglet just barely poking through from the other side and Sans laughed, ducking his head to kiss the join between his clavicles.

As he did so, he did as instructed, revelling in the sublime ache that melted into pleasure and back again while he rocked the aglet in place. He was starting to frantically gulp for air as his soul beat furiously, hungry for more, his magic dispersing to flow throughout his body instead of filling the void in his pelvis. He couldn’t help the gasps of effort, the lewd little moans that made him break into a sweat. He could feel the ache build up in his soul and how blindingly blissful it all was, right on the brink, just  _so close…_

“i… i can’t,” he gasped, trying to push further. Tears were stinging at his eye sockets again as he gave another push, trying to ease the angle a little more. The awkward reentry made him squawk and he felt his magic flood down again, desperate for release.

“ye can do it, baby, just a little more,” Red’s voice rumbled encouragingly, when Sans felt a distinct pinch.

He gaped, his soul seizing when he wanted to give in, to let Red do it, but no. He was being encouraging, guiding the way. He felt another pull from the same hole, his sight spotting a little more again as he was so close to the edge that he had stopped to breathe, halting as he felt another tug.

 _“red-!!”_  was his strangled cry as he pushed his finger against the last intrusion, the bone feeling raw and tingly, throbbing in all the right ways. Red encouraged the end out of the other side with another deft tug and he could finally grasp at the aglet between his fingertips. Sans’ joints locked up as his mouth hung open in a silent shriek, leaning forward to bury his tear-streaked face against his lover and clung to him desperately as he came.

Red nuzzled Sans’ skull as it fell to his shoulder, heavy and wet pants marking the end of Sans’ climax. Sans’ body trembled as barely spoken, nonsensical noises left him. His arms suddenly feeling heavy, his fingers clung to Red’s shirt, wanting to stay close and keep Red’s excited magic nearby.

 

Sans’ eye sockets drifted closed once he had relaxed and the last quakes of his orgasm had run its course. He still felt sensitive all over, but Red had taken to calmly stroking his back, rubbing soothing circles into his scapulae and the back of his ribs.

“all good?” Red asked after a moment and a lingering kiss.

Sans tore himself out of the lulled state, realising that Red had taken to cradling him in his arms. Slick still trickled down his spine under his shirt from his soul, but there was no disturbance to the nearly tied lacing connecting all the little spaces just above his tailbone. Flushed and exhausted, Sans wrapped his arms around Red’s shoulders, nestling close and relishing in the shift of magic they shared.

“m’not gonna be able to look at shoelaces the same way ever again,” he muttered, his voice sounding raw. Red snickered to himself but didn’t stop the backrub. Sans grinned at the reaction, giving him a squeeze. “i mean it. we gotta find some velcro, or something’.”

“kinky.”

Sans gave him a weary, half-hearted headbutt to the sternum with a groan.  _“don’t you dare!”_

 

**Author's Note:**

> [ganzooky on twitter](https://twitter.com/ganzooky/status/1095188368151928832) drew a very nice scene from the middle of this fic!! 8D ( **nsfw** )  
> [ravvi from pillowfort](https://www.pillowfort.social/posts/418880) drew a scene from this! ( **NSFW** )
> 
> This is a Secret Santa pressie for [**kaybedon**](https://twitter.com/kaybedon) (on twitter) ;w; I fucking jumped on this idea when I was assigned you and I read your prefs, you have NO IDEA. Also, this was entirely thirst-filled (same kinks!!)...
> 
> Special thanks to [**undertailsoulsex**](https://archiveofourown.org/users/undertailsoulsex/) for beta-reading this for me ;w;!!! ♥


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